This invention relates to a method for coloring synthetic or semisynthetic organic high molecular weight materials with asymmetric thioindigoid compounds. Although it has been hitherto well known to use thioindigoid compounds as dyestuffs for natural organic materials (for example, cotton), it has been scarcely known to use them as colorants for synthetic or semisynthetic organic high molecular weight materials. Recently, brilliant nuance has been desired in colored articles, especially in weaving apparel, and polyester materials colored with ordinary dyestuffs for polyester show a duller hue than the other colored synthetic organic materials (for example, polyacrylonitrile fabrics). Thus, brilliant dyestuffs for polyester materials have been sought.
This is also testified by the invention of "cationic dye-dyeable polyester" that shows more brilliant hue by dyeing with cationic dyes than the ordinary polyester materials dyed with ordinary dyes for polyester. On the other hand, the thioindigoid compounds show brilliant coloring effects but little dyeability for polyester materials, and thus thioindigoid dyes for polyesters have scarcely been known except that unsubstituted thioindigo is applied only in limited uses.
As a result of intensive colorant tests of organic materials on the thioindigoid compounds, we discovered that compounds of formula (I) to be defined hereinbelow color synthetic organic high molecular weight compounds, especially polyester materials, in brilliant nuance with characteristic fluorescence, and thus completed the invention. Besides, recently .alpha.-aminoanthraquinone, the most important intermediate for reddish diperse anthraquinone dyes, has caused difficult problems on environmental pollution because of using a mercury catalyst for manufacturing it. In contrast the thioindigoid compounds used in this invention can be obtained without using mercury and can develop color in more brilliant nuance than the anthraquinone derivatives. We believe therefore that the industrial merit of this invention is great.